In a vehicle or carrier loaded with an internal combustion machine (i.e. engine) and an integrative synchronous generator, a battery can be recharged by the synchronous generator powered by the engine. For the integrative synchronous generator and the engine are co-shafted and the engine usually runs at high speeds so as to drive the vehicle, the back electromotive force (Back-EMF) induced by the integrative synchronous generator would be much larger than the battery voltage at the input end. Hence, without adequate circuit protection or voltage conversion, the recharging voltage upon the battery would damage the battery and the control system as well. In the art, a DC/DC converter is introduced to bridge the synchronous generator and the input power source so as to perform high-low voltage conversion and thereby not to risk the system power source. Referring to FIG. 1, in order to operate the apparatus normally, a start power is needed, but such a power would degrade the conversion of the system power source and also increase the occupation volume and the cost. Further, the accompanying sub-systems or parts shall be rearranged to meet the involvement of the DC/DC converter.
In another prior-art application of the voltage reduction upon the electric vehicles, a pulse-width modulating method is to introduce a reverse current to cancel the recharging current, such that the induced recharging voltage due to hi-speed operation of the motor can be reduced. Thereby, burning down of the controller due to over powering can thus be avoided. However, the aforesaid method may cost the power device to suffer the high-frequency switching. Shortcomings from the high-frequency switching may include the loss of current switching, the reduced lifetime from over-rating and the heat dissipation problem from high-frequency switching.
In a Taiwan Patent No. I244255, the engine speed is used to determine the rotor speed. While the engine speed is at a low-speed state, a driving device is introduced to control the angle-lag current flow of a rectifier so as to increase the magnetic flux as well as the generation capacity. In another Taiwan Patent No. I277288, the state of accelerating of an engine is evaluated by a signal of throttle open angle so as to regulate the output of the generator and thus further to eliminate the occurrence of some meaningless generation run. In addition, in a Taiwan Patent No. I276738, an engine is started by rocking a start motor. As soon as the engine starts, the electricity to the start motor is then terminated, such that the redundant engine rocker run is then avoided. Definitely, all the aforesaid techniques do contribute to resolve the output control problem in the motor.
In an European Patent No. EP1524762 A2, the accelerating of the engine as well as the recipe for the power output control are judged by the turning rate of the throttle. In the disclosure, as soon as the power output is regulated back to a predetermined value, the control on the power output is then reset. In U.S. Pat. No. 8,334,678 B2, the voltage output of the generator is controlled by a voltage control circuit. In U.S. Pat. No. 7,402,968 B2, the angular relationship between the signal of the power device and the rotor is computed by evaluating the torque, the battery voltage, the temperature, the rotor angle and so on. Also, through the timing control upon the switching of the power device, the switching of the power source can be thus adequately regulated.
In all the aforesaid prior art, resorts of hardware circuit designs are used to eliminate the current impulses so as to protect the power elements, and thus the system shutdown or failure caused by the abrupt noise disturbances at the negative end can be avoided. Also, due to the wave form of the output current is positively modified, the efficient power run can be ensured and also the energy loss can be reduced.